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kylckylc
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Implement minimal Python bindings to SyncActionNode
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‎CMakeLists.txt‎

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@@ -29,6 +29,7 @@ option(BTCPP_EXAMPLES "Build tutorials and examples" ON)
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option(BTCPP_UNIT_TESTS "Build the unit tests" ON)
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option(BTCPP_GROOT_INTERFACE "Add Groot2 connection. Requires ZeroMQ" ON)
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option(BTCPP_SQLITE_LOGGING "Add SQLite logging." ON)
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option(BTCPP_PYTHON "Add Python bindings" ON)
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option(USE_V3_COMPATIBLE_NAMES "Use some alias to compile more easily old 3.x code" OFF)
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@@ -134,6 +135,13 @@ if(BTCPP_SQLITE_LOGGING)
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list(APPEND BT_SOURCE src/loggers/bt_sqlite_logger.cpp )
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endif()
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if(BTCPP_PYTHON)
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find_package(Python COMPONENTS Interpreter Development)
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find_package(pybind11 CONFIG)
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pybind11_add_module(btpy_cpp src/python_bindings.cpp)
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target_link_libraries(btpy_cpp PRIVATE ${BTCPP_LIBRARY})
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endif()
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######################################################
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if (UNIX)

‎python_examples/btpy.py‎

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#!/usr/bin/env python3
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"""
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Top-level module of the BehaviorTree.CPP Python bindings.
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"""
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from btpy_cpp import * # re-export
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def ports(inputs=[], outputs=[]):
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"""Decorator to specify input and outputs ports for an action node."""
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def specify_ports(cls):
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cls.input_ports = list(inputs)
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cls.output_ports = list(outputs)
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return cls
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return specify_ports

‎python_examples/ex01_sample.py‎

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#!/usr/bin/env python3
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"""
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Demo adapted from [1].
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To run, ensure that the `btpy_cpp` Python extension is on your `PYTHONPATH`
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variable. It is probably located in your build directory if you're building from
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source.
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[1]: https://github.com/BehaviorTree/btcpp_sample
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"""
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from btpy import BehaviorTreeFactory, SyncActionNode, NodeStatus, ports
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xml_text = """
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<root BTCPP_format="4" >
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<BehaviorTree ID="MainTree">
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<Sequence name="root">
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<AlwaysSuccess/>
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<SaySomething message="this works too" />
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<ThinkWhatToSay text="{the_answer}"/>
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<SaySomething message="{the_answer}" />
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</Sequence>
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</BehaviorTree>
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</root>
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"""
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@ports(inputs=["message"])
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class SaySomething(SyncActionNode):
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def tick(self):
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msg = self.get_input("message")
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print(msg)
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return NodeStatus.SUCCESS
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@ports(outputs=["text"])
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class ThinkWhatToSay(SyncActionNode):
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def tick(self):
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self.set_output("text", "The answer is 42")
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return NodeStatus.SUCCESS
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factory = BehaviorTreeFactory()
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factory.register(SaySomething)
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factory.register(ThinkWhatToSay)
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tree = factory.create_tree_from_text(xml_text)
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tree.tick_while_running()

‎python_examples/ex02_generic_data.py‎

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#!/usr/bin/env python3
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"""
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Demonstration of passing generic data between nodes.
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To run, ensure that the `btpy_cpp` Python extension is on your `PYTHONPATH`
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variable. It is probably located in your build directory if you're building from
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source.
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"""
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import numpy as np
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from btpy import BehaviorTreeFactory, SyncActionNode, NodeStatus, ports
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xml_text = """
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<root BTCPP_format="4" >
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<BehaviorTree ID="MainTree">
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<Sequence name="root">
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<AlwaysSuccess/>
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<Rotate position="[1.0, 0.0]" theta="90." out="{rotated}" />
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<Translate position="{rotated}" offset="[0.1, 0.1]" out="{translated}" />
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<Print value="{translated}" />
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</Sequence>
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</BehaviorTree>
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</root>
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"""
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@ports(inputs=["position", "theta"], outputs=["out"])
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class Rotate(SyncActionNode):
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def tick(self):
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# Build a rotation matrix which rotates points by `theta` degrees.
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theta = np.deg2rad(self.get_input("theta"))
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c, s = np.cos(theta), np.sin(theta)
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M = np.array([[c, -s], [s, c]])
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# Apply the rotation to the input position.
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position = self.get_input("position")
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rotated = M @ position
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# Set the output.
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self.set_output("out", rotated)
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return NodeStatus.SUCCESS
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@ports(inputs=["position", "offset"], outputs=["out"])
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class Translate(SyncActionNode):
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def tick(self):
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offset = np.asarray(self.get_input("offset"))
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# Apply the translation to the input position.
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position = np.asarray(self.get_input("position"))
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translated = position + offset
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# Set the output.
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self.set_output("out", translated)
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return NodeStatus.SUCCESS
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@ports(inputs=["value"])
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class Print(SyncActionNode):
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def tick(self):
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print(self.get_input("value"))
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return NodeStatus.SUCCESS
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factory = BehaviorTreeFactory()
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factory.register(Rotate)
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factory.register(Translate)
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factory.register(Print)
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tree = factory.create_tree_from_text(xml_text)
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tree.tick_while_running()

‎src/python_bindings.cpp‎

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#include <memory>
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#include <pybind11/pybind11.h>
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#include <pybind11/gil.h>
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#include <pybind11/eval.h>
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#include <pybind11/chrono.h>
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#include <pybind11/pytypes.h>
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#include <pybind11/stl.h>
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#include "behaviortree_cpp/basic_types.h"
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#include "behaviortree_cpp/bt_factory.h"
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#include "behaviortree_cpp/action_node.h"
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#include "behaviortree_cpp/tree_node.h"
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namespace BT
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{
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namespace py = pybind11;
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class Py_SyncActionNode : public SyncActionNode
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{
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public:
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Py_SyncActionNode(const std::string& name, const NodeConfig& config) :
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SyncActionNode(name, config)
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{}
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NodeStatus tick() override
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{
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py::gil_scoped_acquire gil;
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return py::get_overload(this, "tick")().cast<NodeStatus>();
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}
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py::object Py_getInput(const std::string& name)
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{
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py::object obj;
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getInput(name, obj);
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return obj;
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}
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void Py_setOutput(const std::string& name, const py::object& value)
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{
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setOutput(name, value);
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}
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};
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// Add a conversion specialization from string values into general py::objects
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// by evaluating as a Python expression.
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template <>
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inline py::object convertFromString(StringView str)
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{
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try
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{
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// First, try evaluating the string as-is. Maybe it's a number, a list, a
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// dict, an object, etc.
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return py::eval(str);
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}
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catch (py::error_already_set& e)
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{
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// If that fails, then assume it's a string literal with quotation marks
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// omitted.
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return py::str(str);
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}
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}
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PYBIND11_MODULE(btpy_cpp, m)
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{
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py::class_<PortInfo>(m, "PortInfo");
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m.def("input_port",
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[](const std::string& name) { return InputPort<py::object>(name); });
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m.def("output_port",
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[](const std::string& name) { return OutputPort<py::object>(name); });
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m.def(
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"ports2",
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[](const py::list& inputs, const py::list& outputs) -> auto {
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return [](py::type type) -> auto { return type; };
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},
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py::kw_only(), py::arg("inputs") = py::none(), py::arg("outputs") = py::none());
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py::class_<BehaviorTreeFactory>(m, "BehaviorTreeFactory")
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.def(py::init())
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.def("register",
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[](BehaviorTreeFactory& factory, const py::type type) {
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const std::string name = type.attr("__name__").cast<std::string>();
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TreeNodeManifest manifest;
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manifest.type = NodeType::ACTION;
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manifest.registration_ID = name;
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manifest.ports = {};
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manifest.description = "";
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const auto input_ports = type.attr("input_ports").cast<py::list>();
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for (const auto& name : input_ports)
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{
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manifest.ports.insert(InputPort<py::object>(name.cast<std::string>()));
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}
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const auto output_ports = type.attr("output_ports").cast<py::list>();
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for (const auto& name : output_ports)
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{
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manifest.ports.insert(OutputPort<py::object>(name.cast<std::string>()));
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}
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factory.registerBuilder(
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manifest,
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[type](const std::string& name,
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const NodeConfig& config) -> std::unique_ptr<TreeNode> {
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py::object obj = type(name, config);
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// TODO: Increment the object's reference count or else it
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// will be GC'd at the end of this scope. The downside is
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// that, unless we can decrement the ref when the unique_ptr
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// is destroyed, then the object will live forever.
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obj.inc_ref();
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return std::unique_ptr<Py_SyncActionNode>(
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obj.cast<Py_SyncActionNode*>());
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});
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})
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.def("create_tree_from_text",
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[](BehaviorTreeFactory& factory, const std::string& text) -> Tree {
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return factory.createTreeFromText(text);
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});
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py::class_<Tree>(m, "Tree")
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.def("tick_once", &Tree::tickOnce)
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.def("tick_exactly_once", &Tree::tickExactlyOnce)
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.def("tick_while_running", &Tree::tickWhileRunning,
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py::arg("sleep_time") = std::chrono::milliseconds(10));
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py::enum_<NodeStatus>(m, "NodeStatus")
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.value("SUCCESS", NodeStatus::SUCCESS)
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.value("FAILURE", NodeStatus::FAILURE)
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.value("IDLE", NodeStatus::IDLE)
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.value("RUNNING", NodeStatus::RUNNING)
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.value("SKIPPED", NodeStatus::SKIPPED)
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.export_values();
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py::class_<NodeConfig>(m, "NodeConfig");
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py::class_<Py_SyncActionNode>(m, "SyncActionNode")
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.def(py::init<const std::string&, const NodeConfig&>())
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.def("tick", &Py_SyncActionNode::tick)
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.def("get_input", &Py_SyncActionNode::Py_getInput)
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.def("set_output", &Py_SyncActionNode::Py_setOutput);
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}
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} // namespace BT

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